1. Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA 94720-3370, USA.
2. Viral Epidemiology and Immunity Unit, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-3203, USA.
3. Sustainable Sciences Institute, Managua 14007, Nicaragua.
4. Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia, Ministry of Health, Managua 16064, Nicaragua.
5. Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI 48109-2029, USA.
6. Department of Biostatistics, University of Washington, Seattle, WA 98195-1617, USA.
7. Vaccine and Infectious Diseases Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA.
8. Centro de Salud Sócrates Flores Vivas, Ministry of Health, Managua 12014, Nicaragua.